One of ESA's Swarm satellites could be in the path of a speeding piece of space junk.

ESA-P. Carril, 2013

A European Space Agency satellite risks colliding with a piece of space debris about 15 centimeters (a half-foot) long this week, forcing ESA's flight control to plan a rare evasive maneuver.

A piece of an old Russian satellite called Cosmos-375 is forecast to miss Swarm-B, one of ESA's three Swarm satellites that measure Earth's magnetic fields, by just over the length of a football field. But the margin of error for that forecast is around 1,000 meters (3,280 feet or more like three football fields).

ESA has been working with data from the US armed forces' Joint Space Operations Center (JSpOC), located at Vandenberg Air Force base in California, to plan a collision avoidance maneuver that would be uploaded to the satellite Wednesday.

If the satellite is able to alter its orbit as planned, the piece of junk should pass 746 meters (2,448 feet) in front of Swarm-B and 56 meters (184 feet) below it.

"In other words, we see that conducting the planned maneuver would be sufficient to reduce the risk to acceptable levels," ESA's Tim Flohrer said in a blog update on the situation.

Most space debris is made up of pieces of older, man-made satellites that are no longer in operation.

JSpOC and others track well over a half million pieces of space junk small as just a couple of centimeters as they orbit us and sometimes cause problems. Last year, a particle just a few millimeters long is believed to have damaged ESA's Sentinel-1A radar satellite when it dinged it at on orbital velocity of about 40,000 kilometers per hour (about 25,000 mph).

Scientists are working on a number of ways to address the broader problem, including lasers, but for this week the hope is that simply moving the satellite out of the way should be enough to prevent the problem from getting worse.

We should know if that worked after the piece of junk makes its close pass at 3:10 p.m. PT Wednesday. Fingers crossed.